JP7228919B2 - Liquid coating device - Google Patents

Description

The present invention relates to a liquid coating device.

2. Description of the Related Art A liquid coating apparatus is known that discharges a liquid supplied from a liquid reservoir onto a material to be coated. In such a liquid applying apparatus, the liquid in the liquid chamber is discharged by changing the volume of the liquid chamber. As an example of the liquid applicator, Patent Document 1 discloses an applicator that discharges the liquid from a nozzle by changing the volume of a liquid chamber containing the liquid using a flexible plate that is deformed by driving a piezoelectric element. disclosed.

Japanese publication: JP 2016-59863

In the case of a configuration in which the liquid in the liquid chamber is ejected from the nozzle as in the configuration disclosed in Japanese Patent Application Laid-Open No. 2002-200001, the liquid may leak from the nozzle at a timing other than the timing at which the liquid is ejected from the nozzle. Therefore, a configuration has been considered in which a negative pressure regulator such as a negative pressure pump is used to apply negative pressure to a liquid reservoir that supplies liquid into the liquid chamber, thereby preventing the liquid from leaking out of the nozzle. .

However, in the case of the configuration in which the negative pressure is applied to the liquid in the liquid reservoir by the negative pressure regulator, it takes time for the pressure in the liquid reservoir to reach a predetermined negative pressure. Therefore, the liquid may leak from the nozzle until the pressure in the liquid reservoir reaches the predetermined negative pressure. On the other hand, if the negative pressure in the liquid reservoir is higher than the predetermined negative pressure, air may enter the liquid chamber when the liquid is drawn into the liquid chamber from the nozzle.

Further, when a negative pressure is generated by a negative pressure regulator such as a negative pressure pump, pressure pulsation occurs due to the negative pressure regulator. It takes time to stabilize the pressure.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid coating apparatus capable of quickly reducing the pressure in a liquid reservoir that supplies liquid to an ejection section that ejects liquid to a predetermined negative pressure.

A liquid applying apparatus according to an embodiment of the present invention includes a liquid storage section that stores liquid, a liquid remaining amount detection section that detects the amount of liquid remaining in the liquid storage section, and the liquid in the liquid storage section to the outside. a discharge part that discharges, a negative pressure generating part that generates a negative pressure lower than atmospheric pressure, a negative pressure adjusting container whose interior is adjusted to a predetermined negative pressure by the negative pressure generating part, and the liquid remaining amount detecting part a negative pressure generation control unit for controlling the driving of the negative pressure generation unit based on the detection result of; and

According to the liquid applying apparatus according to the embodiment of the present invention, the pressure inside the liquid reservoir that supplies the liquid to the ejection section that ejects the liquid can be quickly reduced to a predetermined negative pressure.

FIG. 1 is a diagram showing a schematic configuration of a liquid coating device according to an embodiment. FIG. 2 is an enlarged view showing the schematic configuration of the discharge section. FIG. 3 is a flow chart showing an example of the operation of the liquid coating device. FIG. 4 is a view corresponding to FIG. 1 of a liquid coating device according to another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated. In addition, the dimensions of the constituent members in each drawing do not faithfully represent the actual dimensions of the constituent members, the dimensional ratios of the respective constituent members, and the like.

(Liquid Coating Apparatus) FIG. 1 is a diagram schematically showing a schematic configuration of a liquid coating apparatus 1 according to an embodiment of the present invention. FIG. 2 is a flow chart showing the operation of the liquid coating apparatus 1. FIG.

The liquid coating device 1 is an inkjet type liquid coating device that ejects a liquid in the form of droplets to the outside. Examples of the liquid include solder, thermosetting resin, ink, and coating liquid for forming a functional thin film (orientation film, resist, color filter, organic electroluminescence, etc.).

The liquid coating device 1 includes a liquid storage section 10 , a pressure adjustment section 20 , a discharge section 30 and a control section 60 .

The liquid storage part 10 is a container that stores liquid therein. The liquid storage section 10 supplies the stored liquid to the ejection section 30 . That is, the liquid storage section 10 has an outlet 10 a that supplies the stored liquid to the ejection section 30 . The pressure inside the liquid reservoir 10 is adjusted by the pressure adjuster 20 . The liquid is supplied to the liquid reservoir 10 from a supply port (not shown).

(Pressure Adjusting Part) The pressure adjusting part 20 adjusts the pressure in the liquid reservoir 10 to a positive pressure higher than the atmospheric pressure, a negative pressure lower than the atmospheric pressure, or the atmospheric pressure. By adjusting the pressure in the liquid storage section 10 in this way, as will be described later, the liquid can be stably discharged from the discharge port 32a of the discharge section 30, and the liquid can be prevented from leaking from the discharge port 32a.

Specifically, the pressure adjustment section 20 has a positive pressure generation section 21 , a negative pressure generation section 22 , a pressure switching section 50 , an atmosphere opening section 25 and a pressure sensor 26 .

The positive pressure generator 21 generates a positive pressure higher than the atmospheric pressure. The positive pressure generator 21 has a positive pressure pump 21a. The positive pressure pump 21a is a positive pressure generator that generates a positive pressure higher than the atmospheric pressure.

The negative pressure generator 22 generates a negative pressure lower than the atmospheric pressure. The negative pressure generator 22 has a negative pressure pump 22a and a negative pressure adjusting container 22b.

The negative pressure pump 22a is a negative pressure generator that generates a negative pressure lower than the atmospheric pressure. The pressure inside the negative pressure adjusting container 22b becomes the negative pressure generated by the negative pressure pump 22a. The negative pressure regulating container 22b is located between the negative pressure pump 22a and the second switching valve 24. As shown in FIG. Since the negative pressure generator 22 has the negative pressure adjusting container 22b, the negative pressure generated by the negative pressure pump 22a is equalized to a predetermined negative pressure.

As a result, the pulsation of the negative pressure generated by the negative pressure pump 22a can be reduced, and the negative pressure generator 22 can obtain a stable predetermined negative pressure. Further, as will be described later, even if the output of the negative pressure pump 22a changes according to the detection result of the pressure in the liquid reservoir 10 by the pressure sensor 26, the negative pressure adjustment container 22b causes the negative pressure pump 22a to generate Pulsation of the negative pressure is reduced and a uniform predetermined negative pressure is obtained in the changed negative pressure. Therefore, when the negative pressure generator 22 is connected to the liquid reservoir 10 as will be described later, the pressure in the liquid reservoir 10 can be quickly reduced to a predetermined negative pressure.

The pressure switching section 50 switches the pressure inside the liquid storage section 10 . Specifically, the pressure switching unit 50 switches the pressure in the liquid reservoir 10 between the positive pressure generated by the positive pressure generating unit 21, the predetermined negative pressure in the negative pressure adjusting container 22b, and the atmospheric pressure. That is, the pressure switching unit 50 of the present embodiment can switch the pressure in the liquid reservoir 10 to a predetermined negative pressure in the negative pressure adjusting container 22b using the first switching valve 23 and the second switching valve 24. is.

Specifically, the pressure switching unit 50 has a first switching valve 23 and a second switching valve 24 , and the pressure in the liquid reservoir 10 is changed using the first switching valve 23 and the second switching valve 24 . switch.

Each of the first switching valve 23 and the second switching valve 24 is a three-way valve. That is, each of the first switching valve 23 and the second switching valve 24 has three ports. Three ports of the first switching valve 23 are connected to the liquid reservoir 10 , the positive pressure generating section 21 and the second switching valve 24 . Three ports of the second switching valve 24 are connected to the negative pressure generating section 22 , the atmosphere opening section 25 and the first switching valve 23 .

The first switching valve 23 and the second switching valve 24 connect two of the three ports inside each. In this embodiment, the first switching valve 23 connects the port connected to the positive pressure generating section 21 or the port connected to the second switching valve 24 to the port connected to the liquid reservoir 10 . That is, the first switching valve 23 connects the liquid reservoir 10 by switching between a circuit connected to the positive pressure generator 21 and a circuit connected to the second switching valve 24 . The second switching valve 24 connects the port connected to the negative pressure generating section 22 or the port connected to the atmosphere opening section 25 to the port connected to the first switching valve 23 . That is, the second switching valve 24 is connected to the first switching valve 23 by switching between a circuit connected to the negative pressure generating section 22 and a circuit connected to the atmosphere release section 25 .

Note that the first switching valve 23 and the second switching valve 24 switch connection between ports according to the open/close signal output from the control unit 60 . The switching signal includes a first control signal, a second control signal, a third control signal and a fourth control signal, which will be described later.

Pressure sensor 26 detects the pressure in liquid reservoir 10 . Pressure sensor 26 outputs the detected pressure in liquid reservoir 10 to controller 60 as a pressure signal. The negative pressure detected by pressure sensor 26 changes according to the amount of liquid remaining in liquid reservoir 10 . That is, when the remaining amount of liquid in the liquid storage section 10 decreases, the negative pressure detected by the pressure sensor 26 becomes higher than when the remaining amount of liquid is large. It should be noted that the increase in the negative pressure means a change from -1 kPa to -1.1 kPa, for example.

Thus, the pressure sensor 26 detects the remaining amount of liquid in the liquid reservoir 10 as the pressure in the liquid reservoir 10 . That is, the pressure sensor 26 is a liquid remaining amount detection section that detects the amount of liquid remaining in the liquid storage section 10 . As a result, the remaining amount of liquid in the liquid reservoir 10 can be detected as the pressure in the liquid reservoir 10, and the detected pressure can be used to control the drive of the negative pressure pump 22a by the controller 60, which will be described later. can.

A control unit 60, which will be described later, controls the driving of the negative pressure pump 22a according to the pressure signal output from the pressure sensor 26. FIG. When the pressure sensor 26 detects a decrease in the remaining amount of liquid in the liquid storage section 10 as a high negative pressure in the liquid storage section 10, the control section 60 sets a low negative pressure target value to reduce the negative pressure. The negative pressure generated by the pressure pump 22a is brought closer to the atmospheric pressure.

With the above configuration, the pressure adjustment unit 20 switches the first switching valve 23 when the pressure inside the liquid reservoir 10 is set to a positive pressure, that is, when the inside of the liquid reservoir 10 is pressurized to a positive pressure. The positive pressure generator 21 and the liquid reservoir 10 are connected. Thereby, the liquid can be pushed out from the liquid storage section 10 to the ejection section 30 . Therefore, the liquid can be stably supplied to the ejection section 30 .

Further, when the pressure in the liquid reservoir 10 is set to a negative pressure, the pressure regulating section 20 switches the second switching valve 24 to connect the negative pressure generating section 22 and the first switching valve 23 and Switching valve 23 is switched to connect second switching valve 24 and liquid reservoir 10 . As a result, the pressure in the liquid reservoir 10 can be set to a predetermined negative pressure in the negative pressure adjusting container 22b, and the liquid can be prevented from leaking out from the ejection port 32a of the ejection section 30. FIG.

Further, when the pressure in the liquid reservoir 10 is set to the atmospheric pressure, the pressure adjustment section 20 switches the second switching valve 24 to connect the atmosphere release section 25 and the first switching valve 23 . At this time, the first switching valve 23 is in a state in which the second switching valve 24 and the liquid reservoir 10 are connected. Thereby, the pressure in the liquid reservoir 10 can be brought to the atmospheric pressure.

As described above, the first switching valve 23 switches the pressure in the liquid reservoir 10 between the positive pressure generated by the positive pressure generator 21 and pressure other than the positive pressure. The second switching valve 24 switches between the atmospheric pressure and the predetermined negative pressure in the negative pressure adjusting container 22b as the pressure other than the positive pressure.

That is, the pressure switching unit 50 includes a first switching valve 23 that switches the pressure in the liquid reservoir 10 between the positive pressure generated by the positive pressure generating unit 21 and a pressure other than the positive pressure, and a pressure other than the positive pressure. and a second switching valve 24 for switching between the atmospheric pressure and the negative pressure in the negative pressure adjusting container 22b. The first switching valve 23 is a first pressure switching section. The second switching valve 24 is a second pressure switching valve.

Thereby, the pressure in the liquid reservoir 10 can be switched between the positive pressure generated by the positive pressure generator 21, the predetermined negative pressure in the negative pressure adjusting container 22b, and the atmospheric pressure. Moreover, since the pressure in the liquid reservoir 10 can be switched between three pressures by means of two switching valves, the pressure in the liquid reservoir 10 can be switched with a small number of parts. As a result, the liquid coating device 1 can be realized with a simple and low-cost configuration.

(Discharging Portion) The discharging portion 30 discharges the liquid supplied from the liquid storing portion 10 to the outside in the form of droplets. FIG. 2 is an enlarged view showing the configuration of the discharge section 30. As shown in FIG. The configuration of the ejection section 30 will be described below with reference to FIG. 2 .

The ejection section 30 has a liquid supply section 31 , a diaphragm 35 and a driving section 40 .

The liquid supply section 31 includes a base member 32 having a liquid chamber 33 and an inflow path 34 therein, and a heating section 36 . A liquid reservoir 10 is positioned on the base member 32 . The inflow path 34 of the base member 32 is connected to the outflow port 10a of the liquid reservoir 10 . The inflow path 34 is connected to the liquid chamber 33 . That is, the inflow path 34 is connected to the liquid chamber 33 and supplies liquid from the liquid reservoir 10 into the liquid chamber 33 . The liquid chamber 33 stores liquid.

The base member 32 has an ejection port 32 a connected to the liquid chamber 33 . The ejection port 32a is an opening for ejecting the liquid supplied into the liquid chamber 33 to the outside. In the present embodiment, since the ejection port 32a opens downward, the liquid supplied to the inflow path 34 and the liquid chamber 33 has a liquid surface protruding downward in the ejection port 32a due to the meniscus.

The heating part 36 is positioned near the inflow path 34 within the base member 32 . The heating unit 36 heats the liquid inside the inflow path 34 . Although not shown, the heating unit 36 has, for example, a plate-shaped heater and a heat transfer block. Note that the heating unit 36 may have other configurations such as a rod-shaped heater or a Peltier element as long as it can heat the liquid in the inflow path.

By heating the fluid in the inflow path 34 with the heating unit 36, the temperature of the fluid can be maintained at a constant temperature higher than room temperature. This can prevent the physical properties of the liquid from changing with temperature.

Although not shown, the liquid coating apparatus 1 may have a temperature sensor for controlling the heating of the heating section 36 near the heating section 36 or near the discharge port 32a. Moreover, the heating part 36 may be positioned on the base member 32 as long as it can heat the fluid in the inflow path 34 .

The diaphragm 35 constitutes part of the wall section that partitions the liquid chamber 33 . The diaphragm 35 is located on the opposite side of the liquid chamber 33 from the ejection port 32a. The diaphragm 35 is supported by the base member 32 so as to be deformable in the thickness direction. The diaphragm 35 constitutes a part of the wall portion that partitions the liquid chamber 33 and changes the volume of the liquid chamber 33 by deformation. As the volume of the liquid chamber 33 changes due to the deformation of the diaphragm 35 in the thickness direction, the liquid in the liquid chamber 33 is discharged from the discharge port 32a to the outside.

The drive unit 40 deforms the diaphragm 35 in the thickness direction. Specifically, the drive unit 40 has a piezoelectric element 41 , a first pedestal 42 , a second pedestal 43 , a plunger 44 , a coil spring 45 and a casing 46 .

The piezoelectric element 41 extends in one direction by applying a predetermined voltage. That is, the piezoelectric element 41 can expand and contract in the one direction. The piezoelectric element 41 deforms the diaphragm 35 in the thickness direction by expanding and contracting in the one direction. The driving force for deforming the diaphragm 35 in the thickness direction may be generated by another driving element such as a magnetostrictive element.

The piezoelectric element 41 of this embodiment has a rectangular parallelepiped shape elongated in the one direction. Although not shown, the piezoelectric element 41 of this embodiment includes a plurality of piezoelectric bodies 41a made of piezoelectric ceramics such as lead zirconate titanate (PZT), which are laminated in one direction and electrically connected to each other. It is configured by connecting to That is, the piezoelectric element 41 has a plurality of piezoelectric bodies 41a laminated in one direction. As a result, the amount of expansion and contraction of the piezoelectric element 41 in the one direction can be increased compared to the case where the piezoelectric element 41 has one piezoelectric body. In addition, the shape of the piezoelectric element is not limited to a rectangular parallelepiped shape, and may be other shapes such as a columnar shape.

The plurality of piezoelectric bodies 41a are electrically connected by side electrodes (not shown) that face each other in a direction that intersects with the one direction. Therefore, the piezoelectric element 41 extends in the one direction by applying a predetermined voltage to the side electrodes. The predetermined voltage applied to the piezoelectric element 41 is a driving signal input from a control section 60 which will be described later.

Since the configuration of the piezoelectric element 41 is the same as that of a conventional piezoelectric element, detailed description thereof will be omitted. Note that the piezoelectric element 41 may have only one piezoelectric body.

The plunger 44 is a rod-shaped member. One axial end of the plunger 44 contacts the diaphragm 35 . The other end of the plunger 44 in the axial direction contacts a first pedestal 42 that covers the end of the piezoelectric element 41 in one direction. That is, the one direction of the piezoelectric element 41 and the axial direction of the plunger 44 match. A plunger 44 is positioned between the piezoelectric element 41 and the diaphragm 35 . The expansion and contraction of the piezoelectric element 41 is thereby transmitted to the diaphragm 35 via the plunger 44 . The plunger 44 is a rod-shaped transmission member.

The other end of plunger 44 is hemispherical. That is, the plunger 44 has a hemispherical tip on the piezoelectric element 41 side. As a result, the expansion and contraction of the piezoelectric element 41 can be reliably transmitted to the diaphragm 35 via the plunger 44 .

The first pedestal 42 covers the end of the piezoelectric element 41 on the side of the diaphragm 35 in the one direction. The first pedestal 42 contacts the plunger 44 . The second pedestal 43 covers the end of the piezoelectric element 41 opposite to the one-directional diaphragm 35 . The second pedestal 43 is supported by a fixed casing bottom wall portion 47a of a fixed casing 47, which will be described later.

The first pedestal 42 and the second pedestal 43 respectively have bottom portions 42a and 43a and vertical wall portions 42b and 43b positioned on the outer peripheral side. The bottoms 42a and 43a each have a size to cover the end surface of the piezoelectric element 41 in one direction. The vertical wall portions 42b and 43b cover part of the side surface of the piezoelectric element 41, respectively.

The first pedestal 42 and the second pedestal 43 are each made of a wear-resistant material. At least one of the first pedestal 42 and the second pedestal 43 may be made of a sintered material to improve wear resistance. Moreover, the hardness of the first pedestal 42 and the hardness of the second pedestal 43 may be different.

The piezoelectric element 41 is housed within a casing 46 . Casing 46 has a stationary casing 47 and a pressurized casing 48 . A pressurized casing 48 is housed within the stationary casing 47 . The piezoelectric element 41 is housed within a pressurized casing 48 . The fixed casing 47 and the pressurized casing 48 are fixed by bolts (not shown) or the like.

The stationary casing 47 has a box shape with an opening on the side of the diaphragm 35 . Specifically, the fixed casing 47 has a fixed casing bottom wall portion 47a and a fixed casing side wall portion 47b.

The fixed casing bottom wall portion 47 a is located on the opposite side of the diaphragm 35 with the piezoelectric element 41 interposed therebetween. The fixed casing bottom wall portion 47a has a hemispherical projecting portion 47c that supports the end portion of the piezoelectric element 41 in one direction. That is, the liquid applying device 1 has a hemispherical protrusion 47c that protrudes in the one direction from the fixed casing bottom wall 47a toward the piezoelectric element 41 and supports the end of the piezoelectric element 41 opposite to the diaphragm 35. have. As a result, the end portion of the piezoelectric element 41 opposite to the diaphragm 35 can be supported by the projecting portion 47c of the fixed casing bottom wall portion 47a without uneven contact. Therefore, the end portion of the piezoelectric element 41 opposite to the diaphragm 35 can be more reliably supported by the fixed casing bottom wall portion 47a.

A second pedestal 43 is positioned between the piezoelectric element 41 and the projecting portion 47c. That is, the liquid applying device 1 has the second pedestal 43 between the piezoelectric element 41 and the projecting portion 47c. As a result, while the end of the piezoelectric element 41 opposite to the diaphragm 35 is held by the second seat 43 , the end of the piezoelectric element 41 opposite to the diaphragm 35 protrudes through the second seat 43 . The portion 47c provides more reliable support.

The pressurized casing 48 is box-shaped with the piezoelectric element 41 interposed therebetween and the side opposite to the diaphragm 35 is open. Therefore, a portion of the fixed casing bottom wall portion 47 a is exposed inside the casing 46 while the pressurized casing 48 is housed inside the fixed casing 47 . In addition, the protrusion 47c described above is positioned at an exposed portion of the fixed casing bottom wall portion 47a.

The pressurized casing 48 has a pressurized casing bottom wall portion 48a and a pressurized casing side wall portion 48b.

The pressurized casing bottom wall portion 48a is located on the diaphragm 35 side. The pressurized casing bottom wall portion 48a has a through hole through which the plunger 44 passes. Therefore, the plunger 44 extends in the one direction between the piezoelectric element 41 and the diaphragm 35 and penetrates the pressurized casing bottom wall portion 48 a to transmit the expansion and contraction of the piezoelectric element 41 to the diaphragm 35 .

The pressurized casing bottom wall portion 48 a is supported by the upper surface of the base member 32 . As a result, the force generated by the later-described coil spring 45 sandwiched between the pressurized casing bottom wall portion 48a and the first pedestal 42 does not act on the diaphragm 35 supported by the base member 32, or acts on the diaphragm 35. very small as well.

Further, the pressurized casing bottom wall portion 48 a holds a coil spring 45 described later between itself and the first pedestal 42 .

The outer surface of the pressurized casing side wall portion 48b contacts the inner surface of the fixed casing side wall portion 47b, and the inner surface of the pressurized casing side wall portion 48b contacts the vertical wall portions 42b and 43b of the first pedestal 42 and the second pedestal 43. Thereby, the first pedestal 42 and the second pedestal 43 can be held by the pressurized casing side wall portion 48b. Therefore, even when a predetermined voltage is applied to the piezoelectric element 41, deformation of the piezoelectric element 41 in the direction orthogonal to the one direction is suppressed.

With the above configuration, the piezoelectric element 41 is sandwiched in the one direction between the plunger 44 and the projecting portion 47c of the fixed casing bottom wall portion 47a. Thereby, when the piezoelectric element 41 expands and contracts in one direction, the expansion and contraction of the piezoelectric element 41 can be transmitted to the diaphragm 35 by the plunger 44 . Therefore, the expansion and contraction of the piezoelectric element 41 can deform the diaphragm 35 in the thickness direction. In FIG. 2, the movement of the plunger 44 due to the expansion and contraction of the piezoelectric element 41 in one direction is indicated by solid arrows.

The coil spring 45 is a spring member spirally extending along the axis in the one direction. The coil spring 45 is sandwiched in the one direction between the first pedestal 42 and the pressurized casing bottom wall portion 48a. A rod-shaped plunger 44 penetrates the coil spring 45 in the axial direction. That is, the first pedestal 42 is positioned between the piezoelectric element 41 and the plunger 44 and coil spring 45 . Also, the coil spring 45 extends along the axis of the plunger 44 between the piezoelectric element 41 and the pressurized casing bottom wall portion 48a.

As a result, the coil spring 45 applies a compressive force in the one direction to the piezoelectric element 41 via the first pedestal 42 . In FIG. 2, the compressive force by the coil spring 45 is indicated by white arrows. It should be noted that the compressive force generated by the coil spring 45 is preferably a force that positions the first pedestal 42 at a position in contact with the plunger 44 when no voltage is applied to the piezoelectric element 41 . For example, the compressive force is preferably 30 to 50% of the force generated in the piezoelectric element 41 when the rated voltage is applied to the piezoelectric element 41 .

Moreover, since the first pedestal 42 is positioned between the piezoelectric element 41 and the plunger 44 and the coil spring 45, the expansion and contraction of the piezoelectric element 41 can be stably transmitted to the plunger 44 via the first pedestal 42. In addition, the compressive force of the coil spring 45 can be stably transmitted to the piezoelectric element 41 via the first pedestal 42 .

Here, when the viscosity of the liquid is high, it is required to operate the piezoelectric element 41 at high speed. Therefore, it is conceivable to improve the responsiveness of the piezoelectric element 41 by inputting a rectangular wave drive signal to the piezoelectric element 41 . In this case, when the piezoelectric element 41 expands and contracts at high speed, the piezoelectric element 41 may expand and contract excessively, causing damage such as peeling inside. In particular, when the piezoelectric element 41 has a plurality of piezoelectric bodies 41a laminated in the expansion/contraction direction, the high-speed operation of the piezoelectric element 41 tends to cause damage such as peeling inside the piezoelectric element 41 . The excessive expansion and contraction of the piezoelectric element 41 means that the amount of expansion and contraction of the piezoelectric element 41 is larger than the maximum expansion and contraction amount when the rated voltage is applied to the piezoelectric element 41 .

On the other hand, by compressing the piezoelectric element 41 in one direction with the coil spring 45 as in the present embodiment, even when a rectangular wave drive signal is input to the piezoelectric element 41, the expansion and contraction of the piezoelectric element 41 It is possible to prevent damage such as detachment from occurring inside the piezoelectric element 41 . That is, the coil spring 45 can suppress excessive expansion and contraction of the piezoelectric element 41 and prevent internal damage due to expansion and contraction of the piezoelectric element 41 . Thereby, the durability of the piezoelectric element 41 can be improved.

Moreover, since the coil spring 45 is positioned between the piezoelectric element 41 and the pressurized casing bottom wall portion 48a as described above, the elastic restoring force of the coil spring 45 can be received by the pressurized casing bottom wall portion 48a. . Therefore, it is possible to prevent deformation of the diaphragm 35 due to the elastic restoring force of the coil spring 45 . Therefore, it is possible to prevent the liquid from leaking from the ejection port 32a and the deterioration of the liquid ejection performance.

In addition, the plunger 44 and the coil spring 45 can be arranged compactly by axially penetrating the coil spring 45 extending spirally along the axis. As a result, the size of the liquid coating device 1 can be reduced.

(Control Unit) Next, the configuration of the control unit 60 will be described below.

The control unit 60 controls driving of the liquid coating device 1 . That is, the control section 60 controls the driving of the pressure adjusting section 20 and the driving section 40 respectively.

The controller 60 has a pressure adjustment controller 61 and a drive controller 62 .

The pressure adjustment control section 61 outputs control signals to the first switching valve 23 and the second switching valve 24 of the pressure adjustment section 20 . The pressure adjustment control unit 61 also outputs a positive pressure pump drive signal to the positive pressure pump 21a. Further, the pressure adjustment control section 61 outputs a negative pressure pump drive signal to the negative pressure pump 22a. The pressure adjustment control section 61 controls the pressure in the liquid reservoir 10 by outputting control signals to the first switching valve 23 and the second switching valve 24 .

For example, when applying positive pressure to the liquid reservoir 10 , the pressure adjustment controller 61 sends a first control signal to the first switching valve 23 to connect the positive pressure generator 21 and the liquid reservoir 10 . to output Further, when negative pressure is applied to the liquid reservoir 10 , the pressure adjustment controller 61 sends a second control signal to the first selector valve 23 to connect the second selector valve 24 and the liquid reservoir 10 . , and outputs a third control signal for connecting the negative pressure generator 22 and the first switching valve 23 to the second switching valve 24 . Further, when the inside of the liquid reservoir 10 is set to atmospheric pressure, the pressure adjustment controller 61 sends a second control signal to the first selector valve 23 to connect the second selector valve 24 and the liquid reservoir 10 . , and outputs a fourth control signal for connecting the atmosphere release portion 25 and the first switching valve 23 to the second switching valve 24 .

The pressure adjustment control section 61 controls the driving of the negative pressure pump 22a according to the pressure signal output from the pressure sensor 26 . That is, if the pressure detected by the pressure sensor 26 does not reach the target negative pressure value even when the negative pressure pump 22a is driven, the pressure adjustment control unit 61 sets the target negative pressure value to a new target negative pressure value. The negative pressure pump 22a is driven according to the value. In this way, when the pressure sensor 26 detects a decrease in the remaining amount of liquid in the liquid reservoir 10 as a high negative pressure in the liquid reservoir 10, the pressure adjustment controller 61 sets the negative pressure target value low. By doing so, the negative pressure generated by the negative pressure pump 22a is brought close to the atmospheric pressure. That is, when the pressure sensor 26 detects a decrease in the amount of liquid remaining in the liquid reservoir 10, the pressure adjustment control section 61 causes the negative pressure generated by the negative pressure pump 22a to approach the atmospheric pressure.

As a result, the pressure inside the liquid reservoir 10 can be set to an appropriate negative pressure according to the amount of liquid remaining in the liquid reservoir 10 . That is, when the remaining amount of liquid in the liquid reservoir 10 is large, the liquid may leak from the ejection section 30 if the negative pressure in the liquid reservoir 10 is too low. On the other hand, when the remaining amount of liquid in the liquid reservoir 10 is small, air may enter the liquid chamber 33 if the negative pressure in the liquid reservoir 10 is too high. On the other hand, with the above-described configuration, the pressure in the liquid reservoir 10 can be set to an appropriate negative pressure that prevents the liquid from leaking from the ejection section 30 and the air from entering the liquid chamber 33 .

The pressure adjustment control section 61 also controls driving of the positive pressure pump 21a. Since the driving of the positive pressure pump 21a is similar to that of the conventional configuration, detailed description thereof will be omitted.

The drive control unit 62 controls driving of the piezoelectric element 41 . That is, the drive control section 62 outputs a drive signal to the piezoelectric element 41 . This drive signal includes an ejection signal.

The ejection signal is a signal for ejecting the liquid in the liquid chamber 33 to the outside from the ejection port 32a by expanding and contracting the piezoelectric element 41 to vibrate the diaphragm 35, as will be described later.

The control unit 60 controls the timing of outputting the ejection signal to the piezoelectric element 41 and the timing of outputting the control signal to the pressure adjustment unit 20 by the drive control unit 62 .

FIG. 3 is a flow chart showing an example of the operation of liquid ejection by the ejection section 30 and pressure adjustment in the liquid storage section 10 by the pressure adjustment section 20 . The control of the timing of outputting the ejection signal to the piezoelectric element 41 and the timing of outputting the control signal to the pressure adjustment unit 20 by the drive control unit 62 of the control unit 60 will be described.

As shown in FIG. 3, first, the controller 60 determines whether or not an external signal instructing ejection has been input (step S1). This external signal is input to the control unit 60 from a controller or the like higher than the control unit 60 .

When an external signal is input to the control unit 60 (YES in step S1), the pressure adjustment control unit 61 of the control unit 60 adjusts the first switching valve 23 of the pressure adjustment unit 20 to positive pressure in step S2. A first control signal that connects generation portion 21 and liquid storage portion 10 is generated and output to first switching valve 23 . The first switching valve 23 is driven according to the first control signal. As a result, the inside of the liquid reservoir 10 is pressurized to a positive pressure. On the other hand, if no external signal is input to the control unit 60 (NO in step S1), the determination in step S1 is repeated until an external signal is input to the control unit 60. FIG.

After step S2, the drive control section 62 of the control section 60 outputs a discharge signal to the piezoelectric element 41 to cause the discharge section 30 to discharge the liquid from the discharge port 32a (step S3).

Note that the pressure adjustment control unit 61 may output the first control signal to the first switching valve 23 after the drive control unit 62 outputs the ejection signal to the piezoelectric element 41 . That is, the ejection from the ejection portion 30 may be performed before the positive pressure is applied to the inside of the liquid storage portion 10 .

After that, the pressure adjustment control section 61 generates a second control signal that connects the second switching valve 24 and the liquid storage section 10 in the first switching valve 23 of the pressure adjusting section 20 , and outputs the second control signal to the first switching valve 23 . do. Further, the pressure adjustment control section 61 generates a third control signal for connecting the atmosphere release section 25 and the first switching valve 23 in the second switching valve 24, and outputs the third control signal to the second switching valve 24 (step S4). . The first switching valve 23 is driven according to the second control signal. The second switching valve 24 is driven according to the third control signal. As a result, the pressure inside the liquid reservoir 10 becomes the atmospheric pressure.

Subsequently, the pressure adjustment control section 61 generates a fourth control signal for connecting the negative pressure generating section 22 and the first switching valve 23 in the second switching valve 24, and outputs it to the second switching valve 24 (step S5). The second switching valve 24 is driven according to the fourth control signal. As a result, the pressure inside the liquid reservoir 10 becomes a negative pressure. Therefore, it is possible to prevent the liquid from leaking out from the ejection port 32 a of the ejection section 30 . After that, this flow ends (END). The control unit 60 repeatedly executes the above-described flow as necessary.

By controlling the pressure in the liquid storage section 10 as described above, the liquid can be stably ejected from the ejection port 32a of the ejection section 30 at an appropriate timing without leakage of the liquid from the ejection port 32a. .

The liquid applying apparatus 1 of the present embodiment includes a liquid reservoir 10 that stores liquid, a pressure sensor 26 that detects the remaining amount of liquid in the liquid reservoir 10, and discharges the liquid in the liquid reservoir 10 to the outside. A discharge part 30, a negative pressure pump 22a that generates a negative pressure lower than the atmospheric pressure, a negative pressure adjustment container 22b whose interior is adjusted to a predetermined negative pressure by the negative pressure pump 22a, and a detection result of the pressure sensor 26. a pressure adjustment control unit 61 that controls the driving of the negative pressure pump 22a, a pressure switching unit 50 that can switch the pressure in the liquid reservoir 10 to the predetermined negative pressure in the negative pressure adjustment container 22b, have

Thereby, the negative pressure generated by the negative pressure pump 22a is equalized in the negative pressure adjusting container 22b. Therefore, the pressure switching unit 50 can quickly switch the pressure in the liquid reservoir 10 to a predetermined negative pressure in the negative pressure adjusting container 22b. In addition, pulsation when negative pressure is generated by the negative pressure pump 22a can also be reduced by the negative pressure adjusting container 22b. As a result, the pressure inside the liquid reservoir 10 can be quickly brought to a predetermined negative pressure.

Moreover, with the above configuration, the negative pressure inside the liquid reservoir 10 can be adjusted according to the amount of liquid remaining in the liquid reservoir 10 . If the negative pressure in the liquid reservoir 10 is too low when the remaining amount of liquid in the liquid reservoir 10 is large, the liquid may leak from the discharge section 30 . On the other hand, if the negative pressure in the liquid reservoir 10 is too high when the remaining amount of liquid in the liquid reservoir 10 is small, air may enter the liquid chamber 33 . On the other hand, with the above-described configuration, the pressure in the liquid reservoir 10 can be set to an appropriate negative pressure that prevents the liquid from leaking from the ejection section 30 and the air from entering the liquid chamber 33 .

Further, in the above-described configuration, the liquid applying apparatus 1 has the negative pressure adjusting container 22b. Therefore, a predetermined negative pressure is obtained by the ratio between the volume of the negative pressure adjusting container 22b and the volume of the flow path connected to the negative pressure adjusting container 22b. It is possible to approach the predetermined negative pressure without exceeding it. That is, the negative pressure adjusting container 22b also has the function of preventing the negative pressure supplied to the liquid reservoir 10 from exceeding the predetermined negative pressure.

In addition, in this embodiment, the liquid coating apparatus 1 further includes a positive pressure generator 21 that generates a positive pressure higher than the atmospheric pressure. The pressure switching unit 50 switches the pressure in the liquid reservoir 10 between the positive pressure generated by the positive pressure generating unit 21, the predetermined negative pressure in the negative pressure adjusting container 22b, and atmospheric pressure.

As a result, the pressure in the liquid reservoir 10 can be switched between a positive pressure that supplies liquid from the liquid reservoir 10 to the ejection section 30 and a negative pressure that prevents the liquid from leaking out of the ejection section 30 . . Therefore, the liquid can be stably ejected from the ejection section 30, and the liquid can be prevented from leaking from the ejection section 30 when the ejection section 30 is not ejecting the liquid.

Since the negative pressure generator 22 has the negative pressure adjusting container 22b as in the present embodiment, the pressure in the liquid reservoir 10 is reduced when the pressure in the liquid reservoir 10 is switched to the negative pressure as described above. can be brought to a predetermined negative pressure quickly and stably.

In the present embodiment, the discharge section 30 includes a liquid chamber 33 to which liquid is supplied, an inflow path 34 connected to the liquid chamber 33 and supplying liquid from the liquid storage section 10 into the liquid chamber 33, the liquid chamber 33 and a diaphragm 35 that changes the volume of the liquid chamber 33 by deformation, and a drive section 40 that deforms the diaphragm 35 in the thickness direction.

In the ejection section 30 having such a configuration, since the amount of liquid ejected from the ejection section 30 is very small, high accuracy is required in the ejection amount and ejection timing of the liquid. Therefore, in the discharge section 30 having the above configuration, it is necessary to control the negative pressure in the liquid storage section 10 with higher accuracy. In the liquid coating apparatus 1 having such a discharge section 30, the negative pressure generating section 22 has the negative pressure adjusting container 22b as in the present embodiment, so that the pressure in the liquid storing section 10 can be quickly and stably adjusted. A predetermined negative pressure can be applied. Therefore, the configuration of the present embodiment is more effective for the liquid coating device 1 having the ejection section 30 configured as described above.

(Other Embodiments) Although the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, without being limited to the above-described embodiment, it is possible to modify the above-described embodiment as appropriate without departing from the spirit thereof.

In the above-described embodiment, the liquid applying apparatus 1 is a so-called ink-jet type liquid applying apparatus that discharges the liquid in the liquid chamber 33 to the outside by changing the volume of the liquid chamber 33 by deforming the diaphragm 35 in the thickness direction. be. However, the liquid applicator may be a so-called nozzle type liquid applicator that ejects liquid from a nozzle according to a change in pressure in a liquid chamber. Further, the configuration of the ejection section of the liquid applying apparatus is not limited to the configuration of the present embodiment, as long as the configuration is such that the liquid in the liquid chamber 33 can be ejected to the outside by deformation of the diaphragm in the thickness direction.

In the above embodiment, the positive pressure generator is the positive pressure pump 21a, and the negative pressure generator is the negative pressure pump 22a. However, the positive pressure generating section may have a configuration other than the pump as long as it can generate positive pressure. The negative pressure generating section may have a configuration other than the pump as long as it can generate negative pressure.

In the above-described embodiment, the pressure adjustment unit 20 includes the first switching valve 23 that switches and connects the circuit connected to the positive pressure generation unit 21 and the circuit connected to the second switching valve 24 to the liquid storage unit 10; It has a second switching valve 24 that switches and connects a circuit connected to the negative pressure generating section 22 and a circuit connected to the atmosphere release section 25 with respect to the switching valve 23 .

However, as shown in FIG. 4, the pressure adjusting section 120 of the liquid applying apparatus 101 has a pressure switching section that connects the positive pressure generating section 21, the negative pressure generating section 22, and the atmosphere opening section 25 to the liquid storing section 10, respectively. 150. In addition, in FIG. 4, the same components as in FIG. 1 are given the same reference numerals, and the description thereof is omitted.

The pressure switching unit 150 has a positive pressure switching valve 121 , a negative pressure switching valve 122 and an atmospheric pressure switching valve 123 . Positive pressure switching valve 121 is positioned between positive pressure generating portion 21 and liquid storing portion 10 . Negative pressure switching valve 122 is positioned between negative pressure generating section 22 and liquid storing section 10 . Atmospheric pressure switching valve 123 is positioned between atmosphere release portion 125 and liquid reservoir 10 . The negative pressure adjusting container 22 b of the negative pressure generating section 22 is located between the negative pressure pump 22 a and the negative pressure switching valve 122 . The positive pressure switching valve 121 , the negative pressure switching valve 122 and the atmospheric pressure switching valve 123 can each be opened and closed according to control signals input from the controller 60 .

The positive pressure switching valve 121 is opened to connect the positive pressure generator 21 and the liquid reservoir 10 when the pressure in the liquid reservoir 10 is made positive, and is otherwise closed. state. Negative pressure switching valve 122 is opened to connect negative pressure generating section 22 and liquid storage section 10 when the inside of liquid storage section 10 is set to a negative pressure, and is closed otherwise. be. The atmospheric pressure switching valve 123 is opened to connect the atmospheric release portion 25 and the liquid reservoir 10 when the inside of the liquid reservoir 10 is set to the atmospheric pressure, and is otherwise closed. .

In the liquid coating apparatus 101 having the configuration described above, the pressure switching unit 150 also switches the pressure in the liquid reservoir 10 between the positive pressure generated by the positive pressure generating unit 21 and the predetermined pressure in the negative pressure adjusting container 22b. can be switched between negative pressure and atmospheric pressure. Further, since the liquid applying apparatus 101 described above also has a negative pressure adjusting container 22b similar to that of the above-described embodiment, the pressure in the liquid reservoir 10 can be rapidly reduced to a predetermined negative pressure. Therefore, the configuration of the liquid applying device 101 also provides the same effects as the configuration of the above-described embodiment.

The pressure adjustment unit is not limited to the configurations shown in FIGS. 1 and 4, and any configuration can be used as long as the positive pressure generation unit, the negative pressure generation unit, and the atmosphere release unit can be connected to the liquid storage unit. You may have such a configuration.

In the above embodiment, the liquid applying apparatus 1 detects the remaining amount of liquid in the liquid reservoir 10 as the pressure in the liquid reservoir 10 by the pressure sensor 26 . However, the liquid applying device may detect the amount of liquid remaining in the liquid remnant portion by other configurations.

In the above-described embodiment, the liquid storage section 10 and the atmosphere opening section can be connected by the pressure adjustment section 20 . However, the pressure adjustment section may have a configuration in which the atmosphere opening section cannot be connected to the liquid storage section. The pressure adjustment section may have any configuration as long as the pressure in the liquid storage section can be set to a predetermined negative pressure in the negative pressure adjustment container.

In the above embodiment, the liquid reservoir 10 and the positive pressure generator 21 can be connected by the pressure adjuster 20 . However, the liquid coating device does not have to have the positive pressure generator. That is, the liquid applying device may control the pressure inside the liquid reservoir by the negative pressure and the atmospheric pressure.

In the above embodiment, the coil spring 45 compresses the piezoelectric element 41 in one direction. However, as long as the piezoelectric element can be compressed in the one direction, the piezoelectric element may be compressed by a structure other than the coil spring. That is, in the above embodiment, the coil spring 45, which is a helical spring member, was used as an example of the compressive force applying unit. However, the helical spring member has a predetermined length and A so-called coiled wave spring in which a wavy wire or flat plate is spirally wound may also be used. Moreover, the compressive force applying portion may have a configuration other than a spiral shape as long as it is configured to compress the piezoelectric element in one direction. It should be noted that the compressive force application section is preferably arranged so as not to interfere with the plunger regardless of the configuration.

INDUSTRIAL APPLICABILITY The present invention can be used for a liquid coating apparatus that ejects liquid from an ejection portion.

1, 101 liquid coating device 10 liquid reservoir 10a outlet 20 pressure adjuster 21 positive pressure generator 21a positive pressure pump (positive pressure generator) 22 negative pressure generator 22a negative pressure pump (negative pressure generator) 22b negative pressure Regulating container 23 First switching valve (first pressure switching section) 24 Second switching valve (second pressure switching section) 25 Atmosphere release section 26 Pressure sensor (remaining liquid level detection section) 30 Discharge section 31 Liquid supply section 32 Base member 32a Discharge port 33 Liquid chamber 34 Inflow passage 35 Diaphragm 36 Heating unit 40 Driving unit 41 Piezoelectric element 41a Piezoelectric body 42 First pedestal 42a Bottom 42b Vertical wall 43 Second pedestal 43a Bottom 43b Vertical wall 44 Plunger 45 Coil spring 46 Casing 47 Fixed casing 47a Fixed casing bottom wall portion 47b Fixed casing side wall portion 47c Protruding portion 48 Pressurized casing 48a Pressurized casing bottom wall portion 48b Pressurized casing side wall portion 50, 150 Pressure switching portion 60 Control portion 61 Pressure adjustment control portion 62 Drive Control unit 121 Positive pressure switching valve 122 Negative pressure switching valve 123 Atmospheric pressure switching valve

Claims (5)

a liquid storage part that stores liquid;
a liquid remaining amount detection unit that detects the amount of liquid remaining in the liquid storage unit;
a discharge section that discharges the liquid in the liquid storage section to the outside;
a negative pressure generating part that generates negative pressure lower than atmospheric pressure;
a negative pressure adjusting container whose interior is adjusted to a predetermined negative pressure by the negative pressure generating unit;
a pressure adjustment control unit that controls driving of the negative pressure generation unit based on the detection result of the remaining liquid amount detection unit;
a pressure switching unit capable of switching the pressure in the liquid reservoir to the predetermined negative pressure in the negative pressure adjusting container ;
The discharge part is
a liquid chamber to which the liquid is supplied;
an inflow passage connected to the liquid chamber and supplying liquid from the liquid reservoir into the liquid chamber;
a diaphragm that constitutes a part of a wall that partitions the liquid chamber and changes the volume of the liquid chamber by deformation;
and a drive unit that deforms the diaphragm in a thickness direction . In the liquid coating device according to claim 1,
further comprising a positive pressure generator that generates a positive pressure higher than atmospheric pressure;
The pressure switching unit switches the pressure in the liquid reservoir between the positive pressure generated by the positive pressure generating unit, the predetermined negative pressure in the negative pressure adjusting container, and atmospheric pressure. Device. In the liquid coating device according to claim 1 or 2,
The pressure adjustment control section brings the negative pressure generated in the negative pressure generating section closer to atmospheric pressure when the remaining liquid amount detection section detects a decrease in the remaining amount of liquid in the liquid storage section. . In the liquid coating device according to any one of claims 1 to 3,
The liquid coating apparatus according to claim 1, wherein the liquid remaining amount detecting section detects the remaining liquid amount in the liquid storing section based on the pressure in the liquid storing section. In the liquid coating device according to claim 2,
The pressure switching part is
a first pressure switching unit that switches the pressure in the liquid reservoir between the positive pressure generated by the positive pressure generating unit and a pressure other than the positive pressure;
and a second pressure switching unit for switching between atmospheric pressure and the predetermined negative pressure in the negative pressure adjusting container as a pressure other than the positive pressure.

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